ZoomLevelFunction (Geotools modules 31-SNAPSHOT API)

Object
- ExpressionAbstract
- - DefaultExpression
  - - FunctionExpressionImpl
    - - ZoomLevelFunction

All Implemented Interfaces:

Expression, Function, FunctionExpression, Factory
```
public class ZoomLevelFunction
extends FunctionExpressionImpl
```
Function that takes a scale denominator and a srid and outputs the zoom level.
Note: EPSG:3857 is currently the only supported srid, and zoom levels are assumed to be at the equator.

Example:
```
 ff.function("zoomLevel",
               ff.function("env", ff.literal("wms_scale_denominator")),
               ff.literal("EPSG:3857")
            );
 
```
The above function would evaluate to the zoomLevel that corresponds to the current environment's wms_scale_denominator, for EPSG:3857.

Example 2:
```
 ff.function("zoomLevel",
               ff.literal(136494.693347),
               ff.literal("EPSG:3857")
            );
 
```
The above function would evaluate to a zoomLevel of 12.

Field Summary

Fields
Modifier and Type	Field	Description
`static double`	`EPSG_3857_O_SCALE`	Scale denominator of the root tile.
`static String`	`MBSTYLE_ROOT_TILE_PIXELS_KEY`	Name of the system variable controlling `ROOT_TILE_PIXELS`
`static FunctionName`	`NAME`
`static int`	`ROOT_TILE_PIXELS`	Number of pixels in the side of the root tile.

Fields inherited from class FunctionExpressionImpl
fallback, functionName, name, params

Fields inherited from interface Expression
NIL

Constructor Summary

Constructors
Constructor Description

ZoomLevelFunction()

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Object`	`evaluate(Object feature)`	Subclass should override, default implementation returns null.
`int`	`getArgCount()`

Methods inherited from class FunctionExpressionImpl
accept, equals, functionName, getExpression, getFallbackValue, getFunctionName, getImplementationHints, getName, getParameters, hashCode, setFallbackValue, setParameters, toString

Methods inherited from class DefaultExpression
isAttributeExpression, isExpression, isFunctionExpression, isGeometryExpression, isLiteralExpression, isMathExpression

Methods inherited from class ExpressionAbstract
evaluate

Methods inherited from class Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface Expression
evaluate

- Field Detail
  - NAME
```
public static final FunctionName NAME
```
  - MBSTYLE_ROOT_TILE_PIXELS_KEY
```
public static final String MBSTYLE_ROOT_TILE_PIXELS_KEY
```
    Name of the system variable controlling ROOT_TILE_PIXELS
    
    See Also:
    
    Constant Field Values
  - ROOT_TILE_PIXELS
```
public static final int ROOT_TILE_PIXELS
```
    Number of pixels in the side of the root tile. Assumes 512 if not otherwise configured.
  - EPSG_3857_O_SCALE
```
public static final double EPSG_3857_O_SCALE
```
    Scale denominator of the root tile. Changes based on the ROOT_TILE_PIXELS value.
- Constructor Detail
  - ZoomLevelFunction
```
public ZoomLevelFunction()
```
- Method Detail
  - getArgCount
```
public int getArgCount()
```
  - evaluate
```
public Object evaluate(Object feature)
```
    Description copied from class: ExpressionAbstract
    
    Subclass should override, default implementation returns null.
    
    Specified by:
    
    evaluate in interface Expression
    
    Overrides:
    
    evaluate in class FunctionExpressionImpl
    
    Returns:
    
    default implementation returns null